Acne is one of the most common skin ailments, occurring in about 80% of people worldwide at some point between adolescence through adulthood.¹ Research shows that acne causes significant negative effects on quality of life, impacting everything from personal to academic and professional life.¹ Phototherapy, either naturally through sunlight or through artificial means, may be a therapeutic option for treating acne. However, while sunlight has been reported as beneficial by many acne patients, care should be taken to avoid prolonged exposure which can exacerbate the condition in some people or worse, lead to development of skin cancer.^2,3

One possible benefit of sunlight for those suffering from acne may be related to its role in the production of vitamin D in our bodies. Though over-exposure to sunlight can cause sunburns, age spots, and other skin damage, sunlight also provides health benefits by enabling our skin to synthesize vitamin D. In fact, foods contain very little vitamin D, so we rely on the sun to make sufficient amounts to maintain bone strength. Emerging evidence suggests that vitamin D may also prevent certain cancers from developing and plays a role in skin health and immunity. Just 20 minutes of sun exposure can generate 10,000 IU of vitamin D—compared to only 400 IU in a quart of fortified milk.^2,4

One of the metabolites of vitamin D, vitamin D3, appears to regulate the expression of cathelicidins—a family of antimicrobial peptides that has been found to be highly protective against Propionibacterium acnes (P. acnes). However, research is still ongoing since these cathelicidins may play an inflammatory immune system role in skin protection.⁵

Some patients claim that sunlight causes a reduction in the severity of acne while others report a worsening of acne symptoms. Although not necessarily related to sunlight exposure, the hot and humid weather of the summer season or tropical regions can also worsen acne by hydrating the keratinous dead skin cells and oils to obstruct the skin pores even more. In a small number of people, excessive exposure to sunlight causes abnormal follicular keratinization which causes a particular type of acne eruption commonly called Mallorca acne.³

Artificial Sunlight—Phototherapy

Based on patient reports of acne improvement from exposure to natural sunlight, studies have been conducted which demonstrate the beneficial effect of phototherapy on acne in controlled environments with exposure to certain wavelengths of light.⁶ Ultraviolet light waves in the 410-420 nanometer wave length kill P. acnes, bacteria that can contribute to the development of acne and the inflammation associated with it.⁷ Results of one randomized, open study involving 60 adult participants suggested that Blue Light therapy utilizing UVB rays at 420 nanometers was better than conventional benzoyl peroxide treatment for moderate to severe acne. Most of the male and female study participants had moderate, or grade II, acne, with a few suffering from grade III acne with more severe inflammation. Randomly divided into two test groups, half the study participants were given Blue Light phototherapy treatments twice a week for four weeks, while half were treated with topical benzoyl peroxide (5%) twice a day for the same time period. The Blue Light group had less lesions and inflammation, as assessed by lesion count and photographic analysis, than the benzoyl peroxide group—with fewer negative side effects.⁶

The Sunscreen Controversy

Some years ago it was suggested that vitamin D deficiency was fairly widespread, which could negatively affect skin health. Although study results are conflicting, research has shown that when used properly most sunscreens completely block UVB rays, which are needed for the photosynthesis of vitamin D in our skin. It is unclear whether this has led to the claimed epidemic of vitamin D deficiency. However, despite any concerns about vitamin D deficiency most experts still caution against lengthy sun exposure without protection. This is because exposure to ultraviolet rays may alter the DNA in skin cells, which can lead to skin cancer and other skin damage.⁷

One solution to achieving optimum levels of vitamin D without unhealthy exposure to the ultraviolet rays from sunshine may be to take vitamin D supplements and to increase consumption of the few foods that contain higher levels of vitamin D (e.g., fatty fish and mushrooms). Dermatologists suggest that this is especially true for those at high risk of skin cancer, which includes those with a family history of this cancer and those with red hair and freckles.⁴

Which Acne Patients Should Avoid Sunlight?

People with rosacea should always avoid sunlight since it is a known trigger to this condition, which is not the same as acne vulgaris (common acne).⁸ Experts suggest that for safety's sake those at high risk of skin cancer should also avoid sunlight (regardless of acne status).⁴ In addition, acne patients who have been recently treated with certain antibiotics or retinoids may be advised to avoid sunlight due to increased photosensitivity associated with these treatments.⁴